1. Field of the Invention
The present invention relates to a recording medium such as high density optical recording medium, i.e., BD-ROM (Blu-ray Disc ROM), which includes copy protection information and an apparatus and methods for forming, recording, reproducing, and restricting reproduction of illegally duplicated recording media.
2. Description of the Related Art
Recently, standardization of Blu-ray Disc Rewritable (BD-RE), which is a new high-density rewritable optical disc capable of recording large capacity high-quality video and audio data, is in progress. BD-RE related products are expected to be available on the market in the near future.
FIG. 1A depicts the structure of a BD-RE, wherein a clamping area, a burst cutting area (BCA), a transition area, a lead-in area, a data area, and lead-out area are disposed in order as shown.
The lead-in area includes several pre-assigned areas such as a first guard (Guard 1) area, a permanent information & control data (PIC) area, a second guard (Guard 2) area, a second (Info 2) and a first information (Info 1) area, and an optimum power calibration (OPC) area. The Guard 1 area and the PIC area are pre-recorded areas in which some initial data is pre-recorded, whereas the other areas of the lead-in area, the data area, and the lead-out areas are all rewritable areas.
The second guard area may be used as a buffer zone for the changeover from the embossed HFM area to the Rewritable area.
The OPC area may be reserved for testing and OPC procedures.
In the PIC area, important permanent disc information is encoded in a wobbled groove by high frequency modulation (HFM). As depicted in FIG. 2, the wobble-shaped data encoding is performed by bi-phase modulation. In this modulation method, a bit with value 0 may be represented by a transition at the start of the bit cell and a bit with value 1 may be represented by a transition at the start and in the middle of the bit cell. The modulated bits may be recorded on the disc by a deviation of the groove from its average centerline as indicated in FIG. 2. The length of each bit cell may be 36T, where T corresponds to the length of a channel bit in the rewritable data areas.
Also, a read-only Blu-ray Disc (BD-ROM) is also under development along with the development of BD-RE. A BD-ROM may include an inner area, a clamping area, a transition area, an information area, and a rim area, as shown in FIG. 3.
The main data of an audio/video (A/V) stream is recorded in the data zone belonging to the information area in an encrypted format using copy protection information (CPI) to help prevent an illegal copy.
Various types of disc information, such as a disc type, may be recorded in the PIC zone belonging to the information area. Where the main data stored in the data zone is encrypted, the CPI for decrypting the data is also recorded in the PIC zone.
Once an optical disc is loaded into an optical disc reproducing apparatus, the optical disc reproducing apparatus detects the CPI recorded in the PIC zone and then decrypts the main data recorded in the data zone, if the main data is stored in an encrypted format.
The CPI protects the contents recorded on the read-only recording medium; hence it is recorded in such a way that it may not be copied to another medium by data copy operations.